Require remote plugin detail before uninstall

[xli-oai]

Summary

• Fetch remote plugin detail before sending the uninstall request.
• Use the detail response to derive the marketplace namespace and plugin name for cache cleanup.
• Stop the uninstall before the backend POST if detail lookup fails, so backend state and local cache state do not diverge.

Testing

• just fmt
• cargo test -p codex-app-server plugin_uninstall
• cargo test -p codex-core-plugins
• git diff --check

[xli-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".